Perhaps you should try some spelling variations:
"international political economy theories" » "international policy economy theories", "international political economic theories", "international political economics theories", "international political economy series"
"national policy ecological services" » "national policy hydrological services", "national policy clinical services", "national policy meteorological services", "national policy psychological services", "national policy economic services", "national social ecological services", "national poverty ecological services"

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: (("national policy ecological services") or ("international political economy theories"))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (("national policy ecological services") OR ("international political economy theories"))*.
• Removing quotes may allow a broader search: (( national policy ecological services ) or ( international political economy theories ))*.